Solenoids use the principal of electromagnetism to produce an electric field for moving an armature of the solenoid in an axial direction. When an electric current is passed through a wounded coil included in the solenoid, an electromagnetic field is produced within the coil. This electromagnetic current is used to axially displace an armature included in the solenoid proximal or distal relative to the coil. Due to their relatively simple operation, solenoids are widely used as actuators for operating valves.
In conventional solenoids, the armature is generally positioned outside of a body of the solenoid coil housing. An armature pin can be coupled to the armature which guides the movement of the armature pin relative to the coil. The axial displacement of the armature towards the coil is generally opposed by a biasing member included in the solenoid configured to urge the armature pin and armature axially distal relative to the coil towards a valve. The electromagnetic field produced by the coil includes axial as well as radial components. While the axial component of the electromagnetic field pulls the armature towards the coil, the radial components tend to twist the armature about an axial axis of the solenoid. The axial movement can misalign the armature increasing friction and possibly causing the armature to be stuck thereby, resulting in the solenoid malfunctioning. To prevent the radial movement of the armature, conventional solenoids include centering shims and chamfered armature pins to prevent axial movement. This complicates the design and manufacturing (and therefore the cost) of the solenoid.